Various kinds of treatment apparatuses are known that comprise a treatment unit to be supplied with a fluid. The known treatment apparatuses include, for example, blood treatment apparatuses. During the blood treatment, the patient's blood flows in an extracorporeal blood circuit through the blood treatment unit. In the case of apparatuses for haemodialysis, haemofiltration and haemodiafiltration, the blood treatment unit is a dialyser or filter, which is divided by a semi-permeable membrane into a blood chamber and a dialysing fluid chamber.
During the dialysis treatment, the blood flows in an extracorporeal blood circuit through the blood chamber, whilst the dialysing fluid flows in a dialysing fluid circuit through the dialysing fluid chamber of the dialyser.
Considering the large exchange quantities, there is a need with the known methods and apparatuses for blood treatment for exact balancing of the fluid removed from the patient and the fluid fed to the patient during the overall treatment time. Gravimetric and volumetric balancing devices belong are known.
A haemodiafiltration apparatus with volumetric balancing is known for example from DE 26 34 238 A1. The balancing device of the known haemodiafiltration apparatus comprises a volume-rigid hollow body, which is divided by a mobile partition wall into two chambers. Each chamber comprises an inlet and an outlet, at which supply lines and discharge lines for fresh and, respectively, used dialysing fluid are disposed, a shut-off element being incorporated in each line. Moreover, provision is made for pumps for conveying the fresh and used dialysing fluid as well as for a control unit, which permits alternate filling of the two chambers.
In order to be able to ensure a continuous flow of dialysing fluid through the dialysing fluid chamber of the dialyser, two balancing chamber are connected in parallel in practice, said balancing chambers supplying the dialyser alternately with fresh dialysing fluid. A balancing unit with two balancing chambers is described in for example DE 28 38 414.
During a dialysis treatment, the dialysing fluid flow typically amounts to 500 ml/min, but can amount to up to 1000 ml/min depending on the given treatment situation. In the case of a dialysis period of 4 hours, this means a dialysing fluid requirement which typically amounts to approx. 120 1, but depending on the given treatment situation can also be over 200 1.
Because of the large fluid requirement in dialysis, the preparation of the dialysate from concentrates and pure water (RO water) in the machine has evolved, in order to avoid the storage of fairly large quantities of solutions. The RO water is made available centrally in the clinic and distributed via lines to the dialysis machines in the dialysis stations.
In the treatment of an acute renal insufficiency, such as can occur for example after accidents, which calls for intensive-care support for the patient, a RO water connection is generally not present. The dialysing fluid is then made available to the machine by means of containers, for example canisters or bags.
In order to keep the handling costs as low as possible, an attempt is made, especially in the case of intensive-care support for acute renal insufficiency, to reduce the requirement for dialysing fluid. This is achieved by the fact that the dialysing fluid is recirculated via the dialyser for a certain length of time. The dialysate requirement can thus be reduced to values which lie below 100 ml/min.
A blood treatment apparatus with a recirculation circuit is known for example from U.S. Pat. No. 5,685, 988. The recirculation of dialysing fluid should however only be used for the determination of blood treatment parameters.
The invention described herein provides a device for conveying fluids into the treatment unit of a medical treatment apparatus, in particular into the dialyser of a dialysis apparatus, with which device the requirement for dialysing fluid can be reduced and a recirculation of dialysing fluid is enabled. Further, the invention described herein provides a method for conveying fluids into the blood treatment unit of a medical treatment apparatus, said method permitting a reduction in the requirement for dialysing fluid and a recirculation of dialysing fluid. The invention described herein also provides an extracorporeal blood treatment apparatus with such a device for conveying fluids.